In today's rapidly advancing semiconductor device manufacturing industry, there is a challenge to continue to increase the size of the wafers used in semiconductor manufacturing while at the same time reducing the dimensions of the device features. In order to reduce the dimensions of device features and spacings, lithography systems that use exposure energies with increasingly lower wavelengths are being utilized because they provide superior pattern resolution. Two examples of such exposure tools used to expose photoresist materials are extreme ultraviolet (EUV) and electron beam direct writing (EDBW) lithography tools. EUV lithography tools utilize extremely short wavelength (typically shorter than about 180 nm) UV radiation and are advantageously used in photolithography to expose ultra-small (below 100 nm) geometries. As opposed to conventional photolithography in which optical lenses are used to direct and shape the light beam, EUV photolithography uses very high precision mirrors for the same purpose. As such, a different mask design is needed for EUV lithography tools. EDBW is distinguished from photolithography as it involves electron beam, i.e. e-beam lithography that uses a focused beam of electrons to expose the resist. No mask is used as a pattern is “written” directly into the resist by scanning of the electron beam. Pattern resolution below 100 nm may be achieved.
The EUV and EDBW lithography tools use extremely low wavelength energy sources with associated high powers to activate the polymers in the photoresist material. The smaller wavelengths allow for an increased resolution to be achieved, such as needed for increased miniaturization of device features and spacings between features, i.e., for smaller critical dimensions. The low wavelength, high power exposure process, however, requires an increase in exposure time and therefore a decrease in throughput of wafers through the exposure operation compared to conventional optical photolithography.
The lower throughput and resulting increase in cycle time is compounded by the increased size of semiconductor wafers now being used in the semiconductor manufacturing industry as the entire surface of the wafer, i.e. each die, must be exposed to the radiation energy. For example, 450 mm wafer sizes are now advantageously being used in the semiconductor manufacturing industry. According to current technologies, when such large wafers are processed through electron beam direct writing exposure systems, the throughput may be less than five wafers per hour. This extremely low throughput level presents a bottleneck in the manufacturing process. Such a low throughput level also increases the cost to manufacture a device because of the increased cycle time and/or the requirement to purchase additional multimillion dollar exposure tools to minimize the impact of the decreased throughput.
It would therefore be desirable to produce semiconductor devices having the requisite feature resolution demanded by current and future technology, with a suitably low cycle time, i.e., it would be desirable to produce semiconductor devices of requisite quality in a faster time.